1. Field of the Invention
This invention relates to a manufacturing method of a solid-state image sensing device in which light-receiving efficiency is improved.
2. Description of the Related Art
In recent years, the solid-state image sensing device such as CCD (charge coupled device) has been used for a cellular phone or a recognizing device, and its application range has been broadening.
An example of a structure of a conventional solid-state image sensing device will be described with reference to drawings.
FIG. 12 is a schematic view of a structure of a conventional solid-state image sensing device employing a frame transfer system. A solid-state image sensing device 1 employing the frame transfer system has an image sensing portion 1i, an accumulating portion 1s, a horizontal transferring portion 1h and an outputting portion 1d. The image sensing portion 1i has a plurality of vertical shift resistors arrayed in parallel to each other in a vertical direction, and each bit of the vertical shift resistors corresponds to each of light-receiving pixels. The accumulating portion 1s has a plurality of the vertical shift resistors connected to the vertical shift resistors forming the image sensing portion 1i. The horizontal transferring portion 1h has horizontal shift resistors arrayed in a column on an output side of the accumulating portion 1s, and each bit of the horizontal shift resistors corresponds to each of the columns of the vertical shift resistors. The outputting portion 1d has a capacitor for receiving information load outputted from the horizontal transferring portion 1h. 
Under this configuration, information load generated at the light-receiving pixels forming the image sensing portion 1i is stored in each of light-receiving regions for a predetermined time, and transferred to the accumulating portion 1s at high speed in response to a frame transfer clock φf. The information load is temporarily accumulated in the accumulating portion 1s, and then sequentially transferred to the horizontal transferring portion 1h line by line in response to a vertical transfer clock φv.
The information load transferred in the horizontal transferring portion 1h is sequentially transferred to the outputting portion 1d pixel by pixel, converted into a voltage value each time, and outputted as a pixel signal Y(t).
FIG. 13 is a plan view of a partial structure of the image sensing portion 1i, and FIG. 14 is a cross-sectional view of FIG. 13 along a line X-X. This structure is constructed as follows.
A P-type diffusing layer 3 to be an element region is formed on a main surface of a N-type silicon substrate 2. On a front surface region of this P-type diffusing layer 3, a plurality of separated regions 4 injected with P-type impurity at a high concentration are disposed in parallel to each other at predetermined intervals. Between the separated regions 4, a plurality of channel regions 5 formed of a N-type diffusing layer is formed, serving as a transfer route of the information load. On the channel regions 5, a plurality of transfer electrodes 7 made of poly-crystallized silicon is disposed in parallel to each other extending in a direction crossing the channel regions 5 with a gate insulating film 6 made of thin silicon oxide interposed between the channel regions 5 and the transfer electrodes 7. Each of these transfer electrodes 7 is applied with frame transfer clocks φf1 to φf3 of three phases, and potential of the channel regions 5 is controlled by these clock pulses.
The transfer electrodes 7 are formed with an interlayer insulating film made of the same material as that of the gate insulating film 6. A plurality of power supply lines 8 made of, for example, aluminum, is formed on the interlayer insulating film so as to cover the separated regions 4. The power supply lines 8 are connected to the transfer electrodes 7 at intersections between the separated regions 4 through the contact hole 11 formed at predetermined intervals in the interlayer insulating film. For example, in three-phase driving, the contact holes 11 are provided at every three transfer electrodes 7, and the power supply lines 8 are connected with the transfer electrodes 7 at every three transfer electrodes 7. An interlayer insulating film 9 is formed so as to cover the power supply lines 8, and a protecting film 10 made of silicon nitride is further formed on this interlayer insulting film 9.
However, in the solid-state image sensing device described above, the power supply lines 8 are formed so as to cover the separated regions 4 on the light-receiving region. A aluminum materials used for the power supply lines 8 generally have characteristics of reflecting light. Therefore, among light incident on the light-receiving region, the light incident on the power supply line 8 is reflected at a front surface of the power supply line 8. Accordingly, the light incident on the power supply line 8 does not enter the channel region 5 so that the information load is not taken in.